Metabolic engineering of plant cell cultures - towards the new resources of alkaloids

Plants produce a wide range of secondary compounds, which have important functions for plants in survival and competing in the ecosystem. One of the major bottlenecks connected with the exploitation of plant cell cultures is that the biosynthetic pathways of secondary compounds are still poorly understood. We have designed a novel technology for unravelling the genes involved in the plant secondary metabolism. This technology called SoluCel® is based on the genome wide identification and functional analysis of genes involved in the production of phytopharmaceuticals in plant cell cultures. The advantage in this technology is that it is applicable to any plant, and no prior knowledge of the gene sequences is required, the fact which very often is encountered when it comes to exotic medicinal plants.
As a model system we used Nicotiana tabacum L. (BY-2) cell culture to unravel the unknown steps involved in nicotine alkaloid biosynthesis. From altogether 591 differentially regulated genes discovered by cDNA-AFLP, 38 were chosen for further functional studies. Of particular interest were the genes encoding for protein kinases, signal transduction proteins, transcription factors and other master regulators.
Full length cDNAs were constructed from cDNA-AFLP tags and were subsequently delivered to Agrobacterium for the establishment of transgenic cell suspension cultures as well as hairy root cultures. The transformed cell lines were subjected to metabolite analysis in order to determine the functional properties of the inserted gene construct. Two genes have resulted in an altered secondary metabolite profile in tobacco hairy roots. Furthermore, the genes derived from tobacco showed potential in altering the secondary metabolite production in related (Hyoscyamus) or non-related (Catharanthus) species. These genes will be further examined to unravel their use when finding novel high-value pharmaceutical compounds from plants.